1. Field of the Invention
This invention relates to an improved gear pump or motor with a shaftless gear and more particularly to an improved gear pump or motor with a shaftless gear having a plurality of gear teeth with a unique tooth profile intermeshing with a gear fixed to a rotatable shaft.
2. Description of the Prior Art
Much effort has been spent in designing gear pumps or motors with a shaftless gear. Such pumps and motors reduce the assembly cost, eliminate some of the manufacturing problems associated with maintaining close tolerances between the gears and the interior of the housing, and of course they reduce the number of needed parts by eliminating at least one gear shaft and its corresponding bearings. Three such gear pumps or motors are described in the following U.S. Pat. Nos. 2,626,570, issued to Armington et al in January, 1953; 3,120,190, issued to Schmitter et al in February, 1964; and 3,286,643, issued to Andrews et al in November, 1966. The major problem with these kinds of pumps or motors is that the shaftless gear is inadequately supported within the housing and therefore tends to rub and wear against an interior surface of the housing. With increased wear, the shaftless gear moves further and further away from the fixed gear. This allows an increased volume of fluid to remain in the gear troughs of the intermeshing gears instead of being forced out of the pump or motor. After the efficiency of the pump or motor drops below a predetermined value, it has to be replaced. By reducing the wear of the gear teeth and the internal surface of the housing, the life of the pump or motor can be extended thereby necessitating less frequent replacement resulting in a cost savings to the owner.
Now an improvement for a gear pump or motor with a shaftless gear has been invented which increases its life expectancy by utilizing a shaftless gear having a unique tooth profile.